(1) Field of the Invention
The present invention relates to an electrostatic recording material. More particularly, the present invention relates to an electrostatic recording material able to be used for an electrostatic plotter for outputting colored images in a computer graphic (CG) system or computer aided design (CAD) system.
(2) Description of the Related Arts
A known electrostatic recording material has an electroconductive layer formed on at least one surface of a support and a dielectric layer formed on the electroconductive layer, and visible images are formed on the electrostatic recording material by applying required voltages from recording electrodes to the surface of the dielectric layer, to form latent images thereon. The latent images are developed with charged toners (consisting of colored fine solid particles or a developing liquid) and the developed colored images are fixed by heating, pressing or drying.
The toners include black, cyan, magenta and yellow-colored toners, and the latent images are converted to visible colored images by repeating the developing operation, with one of the above-mentioned colored toners, and the fixing operation.
Due to recent progress in computer graphics technology, a CAD technology in which various information images including design, external appearance, pattern, and animation images are formed by using a cathode ray tube, (CRT) and output by using a color electrostatic plotter, has been developed.
Also, due to recent progress in scanner technology, an image-outputting system in which images on a manuscript having a size of A3 or smaller are read at an image resolution of 16 dots/mm, by using the scanner, the read images are enlarged to a desired magnification of 12 times or less in each of longitudinal and transversal directions, by utilizing an image treatment technique, and the enlarged images are output by using a color electrostatic plotter, has been developed and is used for preparing posters or advertisements.
When the image-recording material is used outdoors, the recording material usually contains a high strength, water resistant support (substrate) made from a thermoplastic resin film, for example, a polyester or polycarbonate film, or a synthetic paper sheet produced by heat-kneading a mixture of a polyolefin resin, for example, polyethylene or polypropylene resin, with an inorganic pigment, for example, calcium carbonate or sintered clay, melt-extruding the resultant mixture through a film-forming die, drawing the resultant film, and laminating a plurality of the drawn films one upon the other.
The above-mentioned conventional support has a high electrical insulating property, and thus when used as a support of an electrostatic recording material, causes a creation of a lead edge fog (LEF) in preceding side portions of the recording area thereof.
It assumed that the creation of the lead edge fog occurs because, when latent images are formed on the dielectric layer of an electrostatic recording material by using an electrostatic plotter, the electric charge is transmitted through the electroconductive layer and flows into an earthed developing part of the electrostatic plotter.
As an attempt to solve the above-mentioned problem, Japanese Unexamined Patent Publication No. 53-125850 discloses a recording sheet in which at least one side edge portion of the electroconductive layer is exposed to the outside and can be grounded through an electroconductive endless belt arranged in the recording machine. Also, Japanese Unexamined Patent Publication No. 64-6956 discloses the arrangement of a pair of belt-shaped electroconductive layers in both side edge portions of the recording sheet, the belt-shaped electroconductive layers being grounded. The electric resistivity of the belt-shaped electroconductive layers has a close relationship to the intensity of the LEF and should be from 1 .times. 10.sup.4 to 5 .times. 10.sup.5 .OMEGA./cm.
In the colored image recording system, since resistmarks for setting force recording positions are recorded at locations adjacent to the belt-shaped electroconductive layers, a reduction in image density of the resistmarks or defective images of the resistmarks occurs, and thus it becomes impossible to complete the recording operation.